Re: [PATCH v2 1/5] ArmPlatformPkg/FVP: map motherboard VRAM as uncached memory

[Leif Lindholm <leif.lindholm@linaro.org>]

On Thu, Apr 06, 2017 at 07:31:13PM +0100, Ard Biesheuvel wrote:
> On 6 April 2017 at 19:26, Leif Lindholm <leif.lindholm@linaro.org> wrote:
> > On Thu, Apr 06, 2017 at 02:15:47PM +0100, Ard Biesheuvel wrote:
> >> The VRAM of the PL111 on the FVP Base/Foundation models is described as
> >> device memory rather than uncached memory, which is not an accurate
> >> description of the nature of the region (i.e., a framebuffer), and may
> >> result in problems when using accelerated string routines to access the
> >> region, since this may legally involve unaligned accesses or DC ZVA
> >> instructions, which are not allowed on device mappings.
> >>
> >> So split of the 8 MB VRAM region into a separate region, and map it using
> >> memory attributes.
> >
> > "Normal memory attributes"?
> >
> 
> OK
> 
> >>
> >> Contributed-under: TianoCore Contribution Agreement 1.0
> >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> >> ---
> >>  ArmPlatformPkg/ArmVExpressPkg/Include/Platform/RTSM/ArmPlatform.h  | 10 ++++++----
> >>  ArmPlatformPkg/ArmVExpressPkg/Library/ArmVExpressLibRTSM/RTSMMem.c |  8 +++++++-
> >>  2 files changed, 13 insertions(+), 5 deletions(-)
> >>
> >> diff --git a/ArmPlatformPkg/ArmVExpressPkg/Include/Platform/RTSM/ArmPlatform.h b/ArmPlatformPkg/ArmVExpressPkg/Include/Platform/RTSM/ArmPlatform.h
> >> index 06414e6e7208..4e17c800a34f 100644
> >> --- a/ArmPlatformPkg/ArmVExpressPkg/Include/Platform/RTSM/ArmPlatform.h
> >> +++ b/ArmPlatformPkg/ArmVExpressPkg/Include/Platform/RTSM/ArmPlatform.h
> >> @@ -40,9 +40,11 @@
> >>  #define ARM_VE_SMB_SRAM_BASE                    0x2E000000
> >>  #define ARM_VE_SMB_SRAM_SZ                      SIZE_64KB
> >>  // USB, Ethernet, VRAM
> >> -#define ARM_VE_SMB_PERIPH_BASE                  0x18000000
> >> -#define PL111_CLCD_VRAM_MOTHERBOARD_BASE        ARM_VE_SMB_PERIPH_BASE
> >> -#define ARM_VE_SMB_PERIPH_SZ                    SIZE_64MB
> >> +#define ARM_VE_SMB_PERIPH_BASE                  0x18800000
> >> +#define ARM_VE_SMB_PERIPH_SZ                    (SIZE_64MB - SIZE_8MB)
> >> +
> >> +#define PL111_CLCD_VRAM_MOTHERBOARD_BASE        0x18000000
> >> +#define PL111_CLCD_VRAM_MOTHERBOARD_SIZE        SIZE_8MB
> >>
> >>  // DRAM
> >>  #define ARM_VE_DRAM_BASE                        PcdGet64 (PcdSystemMemoryBase)
> >> @@ -75,6 +77,6 @@
> >>  #define PL111_CLCD_CORE_TILE_VIDEO_MODE_OSC_ID  1
> >>
> >>  // VRAM offset for the PL111 Colour LCD Controller on the motherboard
> >> -#define VRAM_MOTHERBOARD_BASE                     (ARM_VE_SMB_PERIPH_BASE   + 0x00000)
> >> +#define VRAM_MOTHERBOARD_BASE                     (PL111_CLCD_VRAM_MOTHERBOARD_BASE)
> >>
> >>  #endif
> >> diff --git a/ArmPlatformPkg/ArmVExpressPkg/Library/ArmVExpressLibRTSM/RTSMMem.c b/ArmPlatformPkg/ArmVExpressPkg/Library/ArmVExpressLibRTSM/RTSMMem.c
> >> index 14c7e8e1d672..70c17ae70478 100644
> >> --- a/ArmPlatformPkg/ArmVExpressPkg/Library/ArmVExpressLibRTSM/RTSMMem.c
> >> +++ b/ArmPlatformPkg/ArmVExpressPkg/Library/ArmVExpressLibRTSM/RTSMMem.c
> >> @@ -21,7 +21,7 @@
> >>  #include <ArmPlatform.h>
> >>
> >>  // Number of Virtual Memory Map Descriptors
> >> -#define MAX_VIRTUAL_MEMORY_MAP_DESCRIPTORS          8
> >> +#define MAX_VIRTUAL_MEMORY_MAP_DESCRIPTORS          9
> >>
> >>  // DDR attributes
> >>  #define DDR_ATTRIBUTES_CACHED   ARM_MEMORY_REGION_ATTRIBUTE_WRITE_BACK
> >> @@ -130,6 +130,12 @@ ArmPlatformGetVirtualMemoryMap (
> >>    VirtualMemoryTable[Index].Length = 2 * ARM_VE_SMB_PERIPH_SZ;
> >>    VirtualMemoryTable[Index].Attributes = ARM_MEMORY_REGION_ATTRIBUTE_DEVICE;
> >>
> >> +  // VRAM
> >> +  VirtualMemoryTable[++Index].PhysicalBase = PL111_CLCD_VRAM_MOTHERBOARD_BASE;
> >> +  VirtualMemoryTable[Index].VirtualBase = PL111_CLCD_VRAM_MOTHERBOARD_BASE;
> >> +  VirtualMemoryTable[Index].Length = PL111_CLCD_VRAM_MOTHERBOARD_SIZE;
> >> +  VirtualMemoryTable[Index].Attributes = ARM_MEMORY_REGION_ATTRIBUTE_UNCACHED_UNBUFFERED;
> >
> > Hmm, looking at this made me a bit confused though. Normal uncached
> > memory is certainly bufferable (that's basically what write-combining
> > means).
> >
> 
> It maps to MAIR attribute encoding 0x44, which translates as
> 
> Normal Memory, Outer Non-Cacheable, Inner Non-Cacheable

Exactly - which is definitely "buffered".

> > This looks like a naming hangover from ARMv5 translation table format.
> > Is it about time we clean this up?
> 
> The whole 'ARM_MEMORY_REGION_xxxx' intermediate namespace should be
> removed, I think.

That sounds like a good idea to me.
There's also _NONSECURE crud in there.

/
    Leif

> > Or have I sprained my brain?
> >
> > /
> >     Leif
> >
> >> +
> >>    // Map sparse memory region if present
> >>    if (HasSparseMemory) {
> >>      VirtualMemoryTable[++Index].PhysicalBase = SparseMemoryBase;
> >> --
> >> 2.9.3
> >>